US Patent 7236597 Key transport in quantum cryptographic networks

Methods, apparatus, and systems are provided for distributing a key between nodes. The nodes are provided separate links for carrying messages versus keying information or material. The links for carrying messages couple the nodes to a messaging network, such as the Internet. In addition, the nodes are coupled together in a key distribution network by specialized links for carrying keying information or material. The links for keying information or material are configured to ensure the security of the keying information or material. The nodes that neighbor each other in the key distribution network establish respective pairwise keys. Once the pairwise keys are established, a set of non-neighboring nodes establish a shared key by communicating a sequence of bits through the messaging network. In order to ensure the security of the sequence of bits, the sequence of bits is encrypted based on the respective pairwise keys of neighboring nodes as it is forwarded in messages through the messaging network.